Corn Bags Are Easy To UseAnd Hold MoistHeat Longer With Even Heat Distribution Over The Entire Bag

Corn is a grain that has a much
larger surface area and holds more moisture. As a
result, it doesn’t dry out as quickly as other natural fillers such as rice, flax seeds, or wheat and retains the heat temperature much longer.

A few issues with other widely used microwavable heating pads

Rice which is naturally a smaller grain may
scorch easily, and has a tendency to turn
rancid and cannot be reheated until it has completely
cooled down.

Flax seed contains 30 to 40% linseed oil which is used in paint thinner and could possibly explode in the presence of oxygen.

Take a look at the safety reports on wheat and other ingredients
used in microwavable heat bags before using.

Scientists have made a statement

"Heating
pads don't just provide comfort and have a placebo effect they actually
deactivate the pain at a molecular level in much the same way as
pharmaceutical painkillers."